The present disclosure relates generally to the electrical, electronic and computer arts and, more particularly, to substrates that facilitate application of a back bias and devices formed using such substrates.
Various methods of fabricating semiconductor-on-insulator substrates such as silicon-on-insulator (SOI) substrates are known, one of which is Separation-by-Implanted Oxygen (SIMOX), wherein oxygen is ion implanted into a single crystal silicon substrate to form a BOX film. Another method of forming an SOI substrate is through the SMART CUT® method and wafer bonding, wherein two semiconductor substrates with silicon oxide surface layers are bonded together at the silicon oxide surfaces to form a BOX layer between the two semiconductor substrates. Doping of SOI substrates can be adjusted during fabrication. Semiconductor substrates such as silicon-on-insulator are commercially available.
The use of SOI substrates without a back gate bias may cause threshold voltage instabilities due to the accumulation of charge from environmental or other sources. This issue may be avoided by applying a bias to the handle substrate, which is comprised of silicon. The application of a back bias may also be used to adjust the threshold voltage of transistors formed on the substrate. Multiple threshold voltage (Vt) devices can be obtained on a single chip by applying different back biases.
Various silicon on transparent, electrically insulating substrates have been developed. Such substrates have potential application to display/pico-projector technologies, for example in mobile applications. Silicon-on-glass (SiOG), silicon on plastic, silicon-on sapphire (SOS) and silicon on quartz (SOQ) are among the electrically insulating substrates that are being used to develop electronic devices. Semiconductor materials other than silicon can alternatively be provided on such substrates. CMOS fabrication techniques have been applied in the fabrication of devices using silicon substrates and some transparent, electrically insulating substrates such as SiOG substrates.